(1) Field of the Invention
This invention relates to electrical connectors which are able to achieve electrical connection only when the conductive means are completely positioned in place in the connector and in which the resilient contact members, which are normally closed to hold said conductive means, are opened during the insertion or extraction of the conductive means so as to eliminate insertion and extraction force on the contacts. The conductive means could for instance consist of an insulating bearer (hard or flexible) carrying electrical circuits comprising conductive layers or strips.
This option becomes more and more important due to the recent development of thin flexible circuits provided with "conductive ink circuits" (CIC).
The conductive layers of these flexible printed circuits are extremely thin and could be damaged by the rubbing against the respective contacts when inserting the boards.
Moreover it is not possible to insert such flexible circuits when the force of insertion exceeds the ability of the flexible circuit to resist buckling.
(2) The Prior Art
Several solutions have already been proposed among which:
(a) the rotary or sliding cam actuated zero insertion force connectors, in which a locking device is used to separate the contact members during insertion or extraction of circuit boards (example: U.S. Pat. No. 3,899,234). PA1 (b) pivotally mounted or sliding member which cooperates with the connector housing to put the contact means therein under tension after insertions (example: MOLEX connector series 4850). PA1 is shaped to be actuated by hand; PA1 is shaped to be actuated by any suitable object or tool; PA1 is shaped to be actuated by a hard circuit board itself.
In the first mentioned solution, the contact members of the connector are in normally closed position. The locking device used to separate said contacts comprises a plurality of parts to be manufactured separately and to be assembled in the connector housing.
In the second solution, the snapping force of the contact members is conditioned by an external member made of plastic material subject to "creep" and to deformations difficult to verify in time.